The present invention relates to a ball given quantity supply apparatus for supplying a given quantity of balls to an apparatus using a given quantity of balls such as a bearing, a ball screw and a linear guide.
Further, the present invention relates to method and apparatus for assembling a ball screw apparatus for use in a feed mechanism employed in various machines.
A ball given quantity supply apparatus of this type is widely known because it is disclosed, for example, in the Examined Japanese Utility Model Application Publication No. Hei1-24025 and the Japanese Patent No. 2991412.
A ball given number take-out apparatus (ball given number supply apparatus) disclosed in the Examined Japanese Utility Model Application Publication No. Hei1-24025 comprises: a hopper 1 in which a plurality of balls W can be stored; a cylindrical-shaped fixed guide 2 fixed to the lower surface of the hopper 1 and extended downwardly therefrom; a collecting tube 4 supported in an internal hole formed in the fixed guide 2 in such a manner that it can be slided in a given range in the upward and downward directions, the collecting tube 4 including a ball passage 3 formed so as to penetrate therethrough in the upward and downward directions; a inducing tube 5 fixed to the upper end portion of the ball passage 3, penetrating through the bottom wall of the hopper 1 so as to be slidable in the upward and downward directions, and projected to the downwardly inclined inner bottom surface of the hopper 1; and, shutter members 6, 7 respectively disposed in the two upper and lower portions of the collecting tube 4, while each of them is able to project and retreat between a projecting position in which it projects into the ball passage 3 to thereby close the ball passage 3 and a retreating position in which it retreats from the ball passage 3 to thereby open the ball passage 3. The shutter members 6, 7 are respectively energized toward their associated retreating positions by their associated spring members 10; however, due to the action of a camportion 8 disposed on the inner peripheral surface of the fixed guide 2, while the collecting tube 4 is being positioned at the lower end position of the above-mentioned given range in the internal hole of the fixed guide 2, the upper shutter member 6 is disposed at the retreating position and the lower shutter member 7 is disposed at the projecting position. Also, while the collecting tube 4 is being positioned at the upper end position of the above-mentioned given range in the internal hole of the fixed guide 2, the upper shutter member 6 is disposed at the projecting position and the lower shutter member 7 is disposed at the retreating position.
While the collecting tube 4 is being disposed at the above lower end position, the lower end portion of the collecting pipe 4 is projected downwardly from the lower end of the internal hole of the fixed guide 2 and the plurality of balls W moved from the inner bottom surface of the hopper 1 into the inducing pipe 5 reach the lower shutter member 7 disposed at the projecting position in the ball passage 3.
And, in case where the lower end portion of the collecting tube 4 at the above-mentioned upper lower end position is pushed upwardly to thereby move the collecting tube 4 up to the above-mentioned upper end position, due to the action of the cam portion 8 of the inner peripheral surface of the fixed guide 2, the lower shutter member 7 is moved to the retreating position and the upper shutter member 6 is moved to the projecting position, so that a given number of balls W in the range of the ball passage 3 between the lower shutter member 7 and upper shutter member 6 are discharged from the end wall of the ball passage 3.
Further, in case where the push-up operation of the lower end portion of the collecting tube 4 at the above upper end position is stopped to thereby move the collecting tube 4 to the above lower end position, due to the action of the camportion 8 of the inner peripheral surface of the fixed guide 2, the lower shutter member 7 is moved to the projecting position and also the upper shutter member 6 is moved to the retreating position, so that a plurality of balls W moved into the inducing tube 5 are allowed to reach again the lower shutter member 7 at the projecting position in the ball passage 3 of the collecting tube 4.
Now, a ball given quantity supply apparatus disclosed in the Japanese Patent No. 2991412 comprises: a ball storage case 21 in which a plurality of balls 23 are stored; an air blow-in portion 22 for blowing the air into the ball storage case 21; a ball supply tube 24 to which the balls 23 are supplied from within the ball storage case 21 by the air blown from the air blow-in portion 22 into the ball storage case 21; and, a rotation block 7 which is disposed on the leading end of the ball supply tube 24 and also which includes a ball storage portion 7a formed so as to penetrate through the rotation block 7 for storing a given number of balls 23 therein. The rotation block 7 is held by and between an upper plate 5 and a lower plate 6. In the upper plate 5, the leading end of the ball supply tube 24 is fixed to a given position on the rotation locus of the upper end of the ball storage portion 7a of the rotation block 7. Also, in the lower plate 6, there is formed a ball discharge hole 6a at a given position on the rotation locus of the lower end of the ball storage portion 7a of the rotation block 7. By the way, the leading end of the ball supply tube 24 at the above given position of the upper plate 5 and the ball discharge hole 6a at the above given position of the lower plate 6 are disposed with the ball storage portion 7a of the rotation block 7 between them, but they are not on a straight line in the vertical direction.
And, while the upper end of the ball storage portion 7a of the rotation block 7 and the leading end of the ball supply tube 24 of the upper plate 5 are disposed on a straight line in the vertical direction, a plurality of balls 23 are supplied from the ball supply tube 24 into the ball storage portion 7a. Next, while the rotation block 7 is rotated so that the upper end of the ball storage portion 7a of the rotation block 7 is shut off from the leading end of the ball supply tube 24 of the upper plate 5 and further the lower end of the ball storage portion 7a and the ball discharge hole 6a of the lower plate 6 are disposed on a straight line in the vertical direction, a given number of balls 23 stored within the ball storage portion 7a are discharged from the ball discharge hole 6a.
[Patent Literature 1]
The Examined Japanese Utility Model Application Publication No. Hei1-24025 (FIGS. 1 to 3)
[Patent Literature 2]
The Japanese Patent No. 2991412 (FIGS. 2 and 3) In the ball given number take-out apparatus (ball given quantity supply apparatus) disclosed in the Examined Japanese Patent Utility Model No. Hei1-24025 and structured and operated in the above-mentioned manner, each time there arises the need to discharge a given quantity of balls W, the collecting tube 4 must be slided by a given distance in the vertical direction within the internal hole of the fixed guide 2; however, this sliding motion of the collecting tube 4 makes it difficult for the given quantity of balls W to be discharged quickly.
Also, in the above ball given quantity take-out apparatus (ball given quantity supply apparatus), each time the collecting tube 4 is slided by a given distance in the vertical direction within the internal hole of the fixed guide 2, the upper end portion of the inducing tube 5 is slided in the vertical direction with respect to the bottom wall of the hopper 1 to thereby allow a plurality of balls W stored in the hopper 1 to flow into the inducing tube 5. However, in this case, there is a possibility that the plurality of balls W in the hopper 1 can concentrate toward the opening of the upper end of the inducing tube 5 and thus can be clogged there. And, such clogging makes it difficult for a given quantity of balls W to be discharged positively. Further, a ball to be supplied to a bearing, a ball screw and a linear guide, in many cases, is covered with oil which has a relatively high coefficient of viscosity, for example, anticorrosive oil; and, in case where such ball is used in the above ball given number take-out apparatus (ball given quantity supply apparatus), the above-mentioned clogging phenomenon is easier to occur.
Further, since the above ball given number take-out apparatus (ball given quantity supply apparatus) does not include device for detecting that a given number of balls are held in the range between the upper and lower shutter members 6 and 7 in the ball passage 3 of the collecting tube 4 while the collecting tube 4 is disposed at the above lower end position, there is a possibility that, although the above-mentioned clogging phenomenon occurs and thus a given number of balls W are not held in the above range, the collecting tube 4 can be slided from the above lower end position to the above upper end position and thus a given number of balls W cannot be discharged from the lower end of the ball passage 3.
In the ball given quantity supply apparatus disclosed in the Japanese Patent No. 2991412, which is structured in the above-mentioned manner and can operate in the above-mentioned manner, supply of the balls 23 from the ball storage case 21 to the ball supply tube 24 by the air blown from the air blow-in portion 22 into the ball storage case 21 becomes unstable in case where the number of balls 23 stored in the ball storage case 21 is small. Also, in case where balls often covered with oil having a relatively high coefficient of viscosity so as to be supplied to a bearing, a ball screw and a linear guide are stored in the ball storage case 21, the above-mentioned supply of the balls from the ball storage case 21 into the ball supply tube 24 by the air blown into the ball storage case 21 from the air blow-in portion 22 can be unstable.
Therefore, in case where the number of balls 23 stored in the ball storage case 21 is small, or in case where balls covered with oil having a relatively high coefficient of viscosity, for example, anticorrosive oil, are stored in the ball storage case 21 in a large number, there is a possibility that the number of balls 23 stored in the ball supply tube 24 can be smaller than the given number of the balls 23 that can be stored into the ball storage portion 7a of the rotation block 7. Due to this, there is a fear that the number of the balls 23 to be discharged through the ball discharge hole 6a of the lower plate 6 from the ball storage portion 7a of the rotation block 7 can be smaller than the above given number.
Further, a ball screw apparatus comprises: a screw shaft and a nut loosely fitted with the screw shaft; the screw shaft includes a spiral-shaped screw groove formed in the outer peripheral surface thereof and extends in the axial direction thereof, and the nut includes a spiral-shaped screw groove corresponding to the spiral-shaped screw groove of the screw shaft; and, the screw groove of the nut and the screw groove of the screw shaft are disposed opposed to each other to thereby form a load passage between the two grooves. A large number of balls serving as rolling bodies are rollably held in the load passage and, to the nut, there is assembled a circulating part such as a circulating tube which allows the balls rolling along the load passage to circulate endlessly. And, in case where the screw shaft (or the nut) is rotated, the nut (or the screw shaft) can be moved in the axial direction through the rolling movements of the balls.
By the way, as a method for assembling the ball screw apparatus of the above type, for example, there is known a method (for example, see patent literature 3 and patent literature 4), in which, with a nut loosely fitted with a screw shaft having a horizontally disposed axial line, a given number of balls inserted into the nut from a ball insertion hole formed in the nut to thereby introduce the balls into a load passage formed between the nut and screw shaft, and, next, the ball insertion hole is closed by a circulating part such as a circulating tube holding the given number of balls therein.
However, in the above method, since the circulating part holding the given number of balls is used to close the ball insertion hole, there is a fear that the balls can fly out from the circulating part and thus the given number of balls cannot be inserted into the nut, that is, there is found a problem in the respect of the operation efficiency.
Thus, as a method which can solve the above problem, for example, there is proposed the following method for assembling a ball screw apparatus (for example, see patent literature 5).
That is, according to the assembling method disclosed in the patent literature 5, a nut, to which a circulating part is previously assembled, is loosely fitted with a provisional shaft having a vertically disposed axial line; after the phase of the ball exit of a ball introduction passage opened up in the interior of the provisional shaft is matched to the highest position of the screw groove of the nut, a given number of balls are passed into the ball introduction passage at the same time to thereby introduce the balls into between the screw groove of the nut and provisional shaft; next, the balls which could not be introduced into between the screw groove and provisional shaft and are left within the ball introduction passage, are pushed into between the screw groove and provisional shaft using a ball push-in rod; and, after completion of the ball insertion operation, the provisional shaft and screw shaft are engaged with each other, and the nut and screw shaft are fitted with each other at the same time when the provisional shaft is removed from the screw shaft.
[Patent Literature 3]
The Examined Japanese Patent Application Publication No. Sho62-22737
[Patent Literature 4]
The Examined Japanese Utility Model Application Publication No. Hei6-50108
[Patent Literature 5]
The Japanese Patent No. 2530401
However, in the ball screw apparatus assembling method disclosed in the patent literature 5, since the balls, which could not be introduced into between the screw groove of the nut and provisional shaft are left in the ball introduction passage, are pushed into between them using the ball push-in rod, there is a fear that the smaller the lead of the screw groove of the nut is, the more easily the balls can be clogged, which makes it difficult to introduce the balls into the nut smoothly.